Milk contains one or more proteins of the globulin group although the amount present is usually quite small. The globulin group is generally considered to be comprised of lactoglobulin or beta lactoglobulin. The globulin of milk is very important. Under certain conditions it enables a mother to transmit immunity toward certain infections to her suckling. This takes place during the first 2 or 3 days of the young animal's life.
During the first few days of lactation, the secretion of the mammary gland differs a great deal from that of normal milk. The secretion is called colostrum. The first colostrum is very rich in globulin and fills the special needs of the newborn animal. Among these is a need for globulin, for the blood of the newborn of many species contains much less than the normal amount of this protein. Colostrum is an important source of antibodies for the newborn. The antibodies may either be the globulins themselves or are associated with the globulins. Colostrum is generally believed to be important in the case of the cow, goat, sheep, pig and mare.